This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Humans throughout history have invented a variety of ways to fight back against troublesome bacteria. But bacteria live in a dangerous world too.
The human body and other bacteria-rich environments abound with bacteriophages, or viruses that prey upon bacteria. Phages can sometimes outnumber bacteria a hundredfold, yet the bacteria endure and even thrive. New research, published in the journal Science Advances, from the Caltech lab of Sujit Datta, professor of chemical engineering, bioengineering and biophysics, helps to explain why.
Among other work, Datta's lab studies bacterial chemotaxis: the movements of microbes in response to chemical stimuli, such as nutrients. To investigate this, the lab has devised experiments in which a dense colony of the gut bacteria Escherichia coli (E. coli), a commonly studied model organism, is deposited in a tube with a kind of "starting line," as in a race. Food—sugar plus an amino acid called L-serine that the bacteria find especially attractive—is placed nearby.
As the bacteria begin to move toward the food, they form "these really cool fronts or coherent bands, almost like a peloton, a group of racers moving together in the Tour de France," Datta explains. The team wondered whether this kind of experiment could help explain how bacteria escape phages in their normal environments, such as biological tissues and soils. Such environments are complex, porous and very difficult to see through.
So, the team, led by Victoria Muir—then a postdoctoral researcher in Datta's lab and now an assistant professor at the University of Delaware—created the bacterial equivalent of an ant farm. The transparent setup consists of a glass tube packed with tiny water-filled beads, or hydrogel, each a few times the size of an E. coli bacterium. When compacted, the beads form a solid mass, but one that is riddled with a maze of channels formed by the gaps between the beads.
Bacteria added to the system have to navigate that maze, similar to how they swim through their natural soil environment, or, in the body, through materials like mucus. For the experiments, E. coli bacteria were genetically modified to glow green under fluorescent light, allowing their movements to be tracked. "We make environments that are structurally more akin to natural habitats of bacteria but are transparent, so we can actually watch the bacteria swimming through," Datta says.
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